U.S. patent application number 13/055294 was filed with the patent office on 2011-06-02 for electrode unit and resistance welding device.
This patent application is currently assigned to ELECTRODE UNIT AND RESISTANCE WELDING DEVICE. Invention is credited to Akihiko Koshido, Takahiro Kunichi, Yoshiki Morishita, Takeomi Okimitsu, Daisuke Sato, Hiroki Sato, Tsuyoshi Yadori.
Application Number | 20110127239 13/055294 |
Document ID | / |
Family ID | 41570316 |
Filed Date | 2011-06-02 |
United States Patent
Application |
20110127239 |
Kind Code |
A1 |
Kunichi; Takahiro ; et
al. |
June 2, 2011 |
ELECTRODE UNIT AND RESISTANCE WELDING DEVICE
Abstract
An electrode unit configuring a resistance welding device is
provided with a first chassis section and a second chassis section.
A plurality of stepped hole sections are formed in the first
chassis section, and an electrode pin is slidably provided in each
stepped hole section. On the head section of the electrode pin, a
resin ball configuring a welding pressure adjusting mechanism is
disposed. In the second chassis section, a screw hole is formed
coaxially with each stepped hole section, and a setscrew
configuring an extrusion output adjusting mechanism for adjusting
an extrusion output of the electrode pin is screwed into each screw
hole.
Inventors: |
Kunichi; Takahiro;
(Saitama-ken, JP) ; Morishita; Yoshiki;
(Saitama-ken, JP) ; Okimitsu; Takeomi;
(Saitama-ken, JP) ; Koshido; Akihiko;
(Saitama-ken, JP) ; Sato; Hiroki; (Saitama-ken,
JP) ; Yadori; Tsuyoshi; (Saitama-ken, JP) ;
Sato; Daisuke; (Saitama-ken, JP) |
Assignee: |
ELECTRODE UNIT AND RESISTANCE
WELDING DEVICE
Tokyo
JP
|
Family ID: |
41570316 |
Appl. No.: |
13/055294 |
Filed: |
July 17, 2009 |
PCT Filed: |
July 17, 2009 |
PCT NO: |
PCT/JP2009/062972 |
371 Date: |
January 21, 2011 |
Current U.S.
Class: |
219/78.01 |
Current CPC
Class: |
B23K 11/115 20130101;
B23K 11/31 20130101; B23K 2101/18 20180801; B23K 2101/36
20180801 |
Class at
Publication: |
219/78.01 |
International
Class: |
B23K 11/00 20060101
B23K011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 23, 2008 |
JP |
2008-189618 |
Claims
1. An electrode unit used in a resistance welder having a pair of
positive and negative electrodes, the resistance welder pressing
and energizing a workpiece by the electrodes to weld the workpiece,
the electrode unit comprising: a case interposed between one of the
electrodes and the workpiece; a plurality of electrode pins
provided in the case, the plurality of electrode pins being
independently movable toward and away from the workpiece to be in
contact with the workpiece for applying an electric current to the
workpiece; a welding pressure adjusting mechanism that
independently adjusts a welding pressure applied on each of the
electrode pins toward the workpiece; and a protrusion adjusting
mechanism that independently adjusts a protrusion of each of the
electrode pins toward the workpiece, wherein the electrode pin is
provided with a contact end touching the workpiece and a head
opposite to the contact end, the head having a slit, the case has
an opening in which the electrode pin is axially slidable and a
slitted opening extending in a radial direction of the head is
provided on an inner wall of the opening, and a metal elastic body
having a bent or curved shape is provided in the slit and the
slitted opening, the metal elastic body pressing the head of the
electrode pin toward the inner wall.
2. The electrode unit according to claim 1, wherein at least a part
of the case is provided by an electroconductive material.
3. (canceled)
4. The electrode unit according to claim 1, wherein the welding
pressure adjusting mechanism comprises an elastic member that is in
contact with the electrode pin to adjust the welding pressure by
elastic deformation.
5. The electrode unit according to claim 1, wherein the welding
pressure adjusting mechanism comprises a spring member that is in
contact with the electrode pin to adjust the welding pressure by
elastic deformation.
6. The electrode unit according to claim 1, wherein the protrusion
adjusting mechanism comprises a screw member that is disposed on an
axis of the electrode pin and allows an adjustment of protrusion of
the electrode pin by adjusting a screwed length.
7. The electrode unit according to claim 5, wherein the protrusion
adjusting mechanism comprises a screw member that is disposed on an
axis of the electrode pin and allows an adjustment of protrusion of
the electrode pin by adjusting a screwed length.
8. The electrode unit according to claim 7, wherein the electrode
pin, the screw member and the spring member are provided by copper
or a copper alloy.
9. An electrode unit used in a resistance welder having a pair of
positive and negative electrodes, the resistance welder pressing
and energizing a workpiece by the electrodes to weld the workpiece,
the electrode unit comprising: a case interposed between one of the
electrodes and the workpiece; a plurality of electrode pins
provided in the case, the plurality of electrode pins being
independently movable toward and away from the workpiece to be in
contact with the workpiece for applying an electric current to the
workpiece; a welding pressure adjusting mechanism that
independently adjusts a welding pressure applied on each of the
electrode pins toward the workpiece; and a protrusion adjusting
mechanism that independently adjusts a protrusion of each of the
electrode pins toward the workpiece, wherein the welding pressure
adjusting mechanism and the protrusion adjusting mechanism comprise
a ball plunger that is disposed on an axis of the electrode pin and
allows an adjustment of the welding pressure and protrusion of the
electrode pin by adjusting a screwed length.
10. A resistance welder, comprising: a pair of positive and
negative electrodes that presses and energizes a workpiece to weld
the workpiece; a pressurizing mechanism that applies a welding
pressure to one of the electrodes; and an electrode unit that is
electrically coupled with the one of the electrodes, wherein the
electrode unit comprises a case interposed between the one of the
electrodes and the workpiece, and the case includes: a plurality of
electrode pins, each of the plurality of electrode pins being
independently movable toward and away from the workpiece to be in
contact with the workpiece for applying an electric current to the
workpiece; a welding pressure adjusting mechanism that
independently adjusts a welding pressure applied on each of the
electrode pins toward the workpiece; and a protrusion adjusting
mechanism that independently adjusts a protrusion of each of the
electrode pins toward the workpiece, wherein the one of the
electrodes has a hemispherical end that is in contact with the
electrode unit.
11. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to an electrode unit used for
a resistance welder (resistance welding device) having a pair of
positive and negative electrodes, the pair of electrodes pressing
and energizing a workpiece under pressure to weld the workpiece,
and a resistance welder.
BACKGROUND ART
[0002] Two or more metal pieces that are mutually layered are often
bonded by a resistance welding, in which the metal pieces are
energized to generate Joule heat to melt the metal pieces while
pressing the metal pieces.
[0003] A plurality of points have to be welded in order to weld,
for instance, a current collecting tab and a current collector of a
battery (e.g. a button battery) or terminals of a circuit board.
Further, in order to provide a separator of a fuel cell, two or
more metal plates are integrally bonded by bonding the metal plates
at a plurality of points.
[0004] When there are concavity and convexity (e.g. embosses) or
steps on a surface of a workpiece in the above welding process, it
is desired to reduce unevenness of the weld strength and the time
required for the welding step.
[0005] In view of the above, a welder and a welding method of an
electroconductive member of a battery are disclosed in Japanese
Laid-Open Publication No. 2002-035945. As shown in FIG. 13, the
welder includes two pressure-side weld electrodes (negative
electrodes) 1a and 1b. The pressure-side weld electrodes 1a and 1b
are respectively attached to electrode holders 3a and 3b each
having welding pressure adjusters 2a and 2b that are capable of
independently adjusting the welding pressure. The pressure-side
weld electrodes 1a and 1b are connected to one of electrodes of a
power source 4.
[0006] On the other hand, a stationary weld electrode (positive
electrode) 6 is disposed on the other side of a workpiece 5 that is
composed of a member 5a and a member 5b. The stationary weld
electrode 6 is connected to the other one of the electrode of the
power source 4.
[0007] With the above arrangement, it is asserted that two points
can be simultaneously welded by the pressure-side weld electrodes
1a and 1b and the welding pressures applied on the pressure-side
weld electrodes 1a and 1b can be equalized by virtue of the welding
pressure adjusters 2a and 2b, so that an even nugget can be
provided.
[0008] However, in order to weld the workpiece 5 at two points,
Japanese Laid-Open Publication 2002-035945 requires that the
pressure-side weld electrodes 1a and 1b, the welding pressure
adjusters 2a and 2b and the electrode holders 3a and 3b have to be
provided as separate components. Thus, the arrangement becomes
complex, thus failing to reduce the size of the entire welder.
[0009] Further, when the workpiece 5 is welded at three or more
points, the pressure-side weld electrodes 1a and 1b cannot
simultaneously weld the three or more target points on the
workpiece 5. Accordingly, it is difficult to apply an even pressure
on each of the welding points.
SUMMARY OF INVENTION
[0010] The present invention is made to overcome the above
deficiencies. An object of the present invention is to provide an
electrode unit having a simple and compact arrangement while
allowing a simultaneous welding of a plurality of welding points
with an even pressure and contact state, and a resistance
welder.
[0011] The present invention relates to an electrode unit used for
a resistance welder, the resistance welder having a pair of
positive and negative electrodes, the pair of electrodes pressing
and energizing a workpiece to weld the workpiece.
[0012] The electrode unit includes: a case interposed between one
of the electrodes and the workpiece; a plurality of electrode pins
provided in the case, the plurality of electrode pins being
independently movable toward and away from the workpiece to be in
contact with the workpiece for applying an electric current to the
workpiece; a welding pressure adjusting mechanism that
independently adjusts a welding pressure applied on each of the
electrode pins toward the workpiece; and a protrusion adjusting
mechanism that independently adjusts a protrusion of each of the
electrode pins toward the workpiece.
[0013] Further, the present invention relates to a resistance
welder including a pair of positive and negative electrodes that
press and energize a workpiece to weld the workpiece.
[0014] The resistance welder includes: a pressurizing mechanism
that applies a welding pressure to one of the electrodes; and an
electrode unit that is electrically coupled with the one of the
electrodes. The electrode unit comprises a case interposed between
the one of the electrodes and the workpiece. The case includes: a
plurality of electrode pins, each of the plurality of electrode
pins being independently movable toward and away from the workpiece
to be in contact with the workpiece for applying an electric
current to the workpiece; a welding pressure adjusting mechanism
that independently adjusts a welding pressure applied on each of
the electrode pins toward the workpiece; and a protrusion adjusting
mechanism that independently adjusts a protrusion of each of the
electrode pins toward the workpiece.
[0015] In the present invention, while being pressed by the one of
the electrodes, a plurality of points are simultaneously welded by
the plurality of electrode pins provided in the case. At this time,
the welding pressure of each of the electrode pins against the
workpiece and the protrusion of each of the electrode pins toward
the workpiece are independently adjusted. Thus, irrespective of the
surface configuration (concavity and convexity; e.g. embosses) of
the workpiece, a plurality of welding points can be favorably
welded at an even pressure and contact state with a simple and
compact arrangement to provide a high-quality welding.
BRIEF EXPLANATION OF DRAWINGS
[0016] FIG. 1 is a side elevational view schematically showing a
resistance welder according to a first embodiment of the present
invention;
[0017] FIG. 2 is a perspective view schematically showing the
resistance welder;
[0018] FIG. 3 is an exploded perspective view showing a separator
to be welded by the resistance welder;
[0019] FIG. 4 is an exploded perspective view showing an electrode
unit of the resistance welder;
[0020] FIG. 5 is a perspective view showing the electrode unit;
[0021] FIG. 6 is an explanatory view showing an electrode pin of
the electrode unit that is in contact with a welding point;
[0022] FIG. 7 is an explanatory view showing a reaction force
applied on the electrode pin;
[0023] FIG. 8 is an exploded perspective view showing a metal plate
to be welded by the resistance welder;
[0024] FIG. 9 is a cross section showing a part of an electrode
unit according to a second embodiment of the present invention;
[0025] FIG. 10 is a cross section showing a part of an electrode
unit according to a third embodiment of the present invention;
[0026] FIG. 11 is a perspective view showing a relevant part of an
electrode unit according to a fourth embodiment of the present
invention;
[0027] FIG. 12 is a plan view showing a relevant part of the
electrode unit; and
[0028] FIG. 13 is an explanatory view showing a welder disclosed in
Japanese Laid-Open Publication No. 2002-35945.
DESCRIPTION OF EMBODIMENTS
[0029] As shown in FIGS. 1 and 2, a resistance welder 10 according
to a first embodiment of the present invention includes a base 12
on which a body 14 is mounted. An upper electrode (one of
electrodes) 18 is attached to the body 14 via a vertical moving
holder 16. A lower electrode 20 is attached to the base 12 so that
the lower electrode 20 is coaxially opposed to the upper electrode
18.
[0030] Provided to the body 14 is a pressurizing mechanism 22 for
moving the vertical moving holder 16 in a vertical direction (a
direction shown by an arrow A) by a manual operation or by an
actuator to apply a welding pressure to the upper electrode 18.
[0031] A base plate 24 is placed on the lower electrode 20 and is
supported by a backup member 26. The base plate 24 is made of
copper or copper alloy such as oxygen-free copper (OFCu) and tough
pitch copper (TCu), and is provided with a recess 30 corresponding
to a shape of a below-described separator 28. An electrode unit 32
electrically connected with the upper electrode 18 is disposed on
the base plate 24.
[0032] The separator 28 serves as a bipolar plate sandwiching an
MEA 34 having an anode and a cathode disposed on both sides of an
electrolyte, the bipolar plate being used in a solid oxide fuel
cell (SOFC), solid polymer electrolyte fuel cell (SPFC),
phosphoric-acid fuel cell (PAFC), molten carbonate fuel cell (MCFC)
and the like (see FIG. 3).
[0033] The separator 28 includes two plates 36 and 38 provided by
metal plates of stainless steel and the like, which are integrated
by resistance welding (spot welding). A fuel gas supply unit 42
defining a fuel gas supply passage 40 is provided at the center of
the plates 36 and 38. Bridge sections 44 radially extend from the
fuel gas supply unit 42 are respectively provided with a fuel gas
supply channel 46 that is in communication with the fuel gas supply
passage 40.
[0034] The fuel gas supply channels 46 radially extend in eight
directions between the plates 36 and 38, and are in communication
with fuel gas supply holes 48 formed on the plate 38 near terminal
ends thereof.
[0035] A plurality of projections 50 to be in contact with the MEA
34 project on the plate 38 around the respective fuel gas supply
holes 48. The plates 36 and 38 are spot-welded at a flat portion
between the projections 50 and have a plurality of welding points
51a at an MEA-sandwiching portion 51 at which each of the MEA 34 is
disposed.
[0036] As shown in FIGS. 4 and 5, the electrode unit 32 is provided
with a first case 52 and a second case 54. The first case 52 and
the second case 54 are disc-shaped. The first case 52 and the
second case 54 are preferably provided by the same
electroconductive material such as copper and copper alloy.
[0037] A plurality of stepped holes 56 are bored in the first case
52. An electrode pin 58 that is in contact with the separator
(workpiece) 28 to apply electric current and is independently
movable toward and away from the separator 28 is disposed in the
stepped holes 56. The number of the electrode pins 58 is determined
in accordance with the number of welding points necessary for the
workpiece. Specifically, the number of the electrode pins 58 is set
equal to the welding points 51a of the respective MEA sandwiching
portions 51.
[0038] The electrode pin 58 is made of copper, copper alloy, copper
tungsten (CuW), chromium copper (CrCu), beryllium copper (Cu--Be),
alumina dispersion strengthened copper (Al.sub.2O.sub.3Cu) or the
like. The electrode pin 58 has a contact end 58a that is inserted
into a smaller-diameter portion of the stepped hole 56 to be
contacted with the separator 28 and a head 58b that is provided
opposite to the contact end 58a and is slidably disposed in a
larger-diameter portion of the stepped hole 56.
[0039] An elastic body such as a resin ball (welding pressure
adjusting mechanism) 60 that is exemplarily made of silicone rubber
and is in contact with the head 58b of the electrode pin 58 for
adjusting the welding pressure to be applied on the separator 28 is
disposed in the large-diameter portion of the stepped hole 56.
[0040] A plurality of threaded holes 62 coaxial with the respective
stepped holes 56 of the first case 52 are provided in the second
case 54. A screw member such as a setscrew (protrusion adjusting
mechanism) 64 for adjusting a protrusion of the electrode pin 58
toward the separator 28 is screwed into the respective threaded
holes 62. The setscrew 64 is provided by a resin material and the
like.
[0041] The first case 52 and the second case 54 are integrally
fastened by a screw 66. An insulating plate 68 provided by Bakelite
and the like is firmly attached to the first case 52. A rectangular
recess 70 for receiving the plurality of projections 50 provided on
the respective MEA sandwiching portions 51 to position the
electrode unit 32 relative to the MEA sandwiching portion 51 is
provided in the insulating plate 68 at a side facing the separator
28. The upper electrode 18 has a semi-spherical end 18a that is in
contact with the electrode unit 32.
[0042] An operation of the electrode unit 32 and the resistance
welder 10 will be described below.
[0043] Initially, as shown in FIG. 2, the plate 36 as a part of the
separator 28 is placed in the recess 30 provided in the base plate
24. The plate 38 is overlaid on the plate 36. The electrode unit 32
is positioned on the plate 38 corresponding to the predetermined
MEA sandwiching portion 51.
[0044] Subsequently, the pressurizing mechanism 22 of the
resistance welder 10 is operated to move the upper electrode 18
downward in conjunction with the vertical moving holder 16. Thus,
the upper electrode 18 contacts with the second case 54 of the
electrode unit 32 to press the electrode unit 32 toward the base
plate 24.
[0045] Consequently, in the electrode unit 32, the contact end 58a
of the respective electrode pins 58 touches the welding point 51a
on the plate 38 (see FIG. 6). While the upper electrode 18 is
pressed downward until a predetermined pressure is reached, the
electrode pins 58 receive a reaction force from the plate 38 (see
an arrow in FIG. 7). At this time, since the resin ball 60 is
disposed on the side of the head 58b of the respective electrode
pins 58, the reaction force applied to the electrode pin 58 is
adjusted by an elastic deformation of the resin ball 60, so that
the welding pressure of the electrode pins 58 is independently
adjusted.
[0046] Subsequently, in the resistance welder 10, the pair of
positive and negative electrodes (i.e. the upper electrode 18 and
the lower electrode 20) feed electric current to the respective
electrode pins 58 through the upper electrode 18 and the electrode
unit 32.
[0047] Thus, in the first embodiment, the plurality of welding
points 51a on the plates 38 and 36 are simultaneously welded via
the plurality of electrode pins 58 provided on the electrode unit
32 under the pressure applied by the upper electrode 18. Hence, a
plurality of points can be welded with a single control system.
[0048] Further, the resin ball 60 is used as the welding pressure
adjusting mechanism for the respective electrode pins 58. Highly
elastic material such as silicone rubber and urethane rubber is
used for the resin ball 60, so that the pressure can be adjusted
over a wide range even in the stepped holes 56 that are formed in a
compact size. Particularly, even when the welding points 51a are
randomly arranged, the pressure can be evenly applied for the
respective electrode pins 58.
[0049] Further, in the first embodiment, the protrusion adjusting
mechanism in the form of the setscrew 64 is screwed to the second
case 54 corresponding to each of the electrode pins 58.
Accordingly, only by adjusting the setscrew 64 for each of the
electrode pins 58, the stroke of the respective electrode pins 58
can be independently and securely adjusted. Thus, even when the
welding points 51a are not located on a flat plane, the respective
points 51a can be appropriately and securely welded.
[0050] Incidentally, the stroke of each of the electrode pins 58
can be adjusted by welding a test sample of the separator 28 in
advance and detecting the welding status of each of the electrode
pins 58.
[0051] According to the first embodiment, without being affected by
a surface profile (concavity and convexity) of the separator 28, a
multiple number of the welding points 51a can be evenly contacted
at an even pressure with a simple and compact arrangement, thus
allowing high-quality welding.
[0052] Further, since a single control system can be used, it is
not necessary to provide a cylinder or a transformer for each of
the electrode pins 58, so that the size and weight of the entire
resistance welder 10 can be easily reduced.
[0053] Further, the first case 52 and the second case 54 in the
first embodiment are made of an electroconductive material such as
copper and copper alloy. Thus, electric current can be applied to
the separator 28 through the upper electrode 18, the second case
54, the first case 52 and the electrode pin 58. In addition, the
resin ball 60 is used as the welding pressure adjusting mechanism
and the setscrew 64 is used as the protrusion adjusting mechanism.
Thus, the arrangement of the electrode unit 32 can be simplified
and economized.
[0054] Further, the end 18a of the upper electrode 18 is
semispherical. Accordingly, when a welding pressure is applied to
the upper electrode 18, the end 18a and the electrode unit 32 can
be kept in contact with each other irrespective of the angle of the
end 18a. Accordingly, the electrode unit 32 can be securely pressed
by the upper electrode 18, so that the respective electrode pins 58
can be securely kept in contact with the separator 28.
[0055] Still further, the first embodiment can be used for welding
two disc-shaped metal plates 72 and 74 as shown in FIG. 8 instead
of the separator 28 as the workpieces. In this arrangement, a base
plate 76 exemplarily has a circular recess 78 corresponding to the
profile of the metal plate 72 and 74.
[0056] The metal plate 72 has a flat shape. On the other hand, the
metal plate 74 has a plurality of embossed portions 80. The metal
plates 72 and 74 are bonded at a plane surrounding the embossed
portions 80 via a plurality of bonding points 51a.
[0057] On the other hand, the electrode unit 32 only requires the
number of electrode pins 58 corresponding to the welding points 51a
of the metal plates 72 and 74. Accordingly, the metal plates 72 and
74 can be easily and securely bonded using the resistance welder 10
by a single control system.
[0058] Incidentally, the metal plates 72 and 74 may be shaped in
various profiles other than the circular profile. According to the
above arrangement, two workpieces, one of which (metal plate 74)
has concavity and convexity (e.g. embossed portions 80), can be
favorably welded at the plurality of welding points 51a.
[0059] FIG. 9 is a cross section showing a part of an electrode
unit 90 according to a second embodiment of the present invention.
It should be noted that the same components as those of the
electrode unit 32 according to the first embodiment will be denoted
by the same reference numerals to omit detailed explanation
thereof. The above also applies to the following third and fourth
embodiments.
[0060] An electrode unit 90 includes a first case 92 and a second
case 54. The first case 92 may be provided by a resin material as
well as an electroconductive material such as copper and copper
alloy. Each of the plurality of stepped holes 56 provided on the
first case 92 receives the electrode pins 58 so that the electrode
pins 58 are independently movable. A welding pressure adjuster 94
is provided near heads 58b of the electrode pins 58.
[0061] The welding pressure adjuster 94 includes a spring member
(e.g. a spring 96) and seats 98a and 98b disposed on upper and
lower ends of the spring 96. The spring 96 and the seats 98a and
98b are provided by an electroconductive member such as copper and
copper alloy.
[0062] In this second embodiment, an elastic deformation of the
spring 96 is used for adjusting the welding pressure of the
electrode pin 58, so that advantages similar to that in the
above-described first embodiment using the resin ball 60 can be
obtained.
[0063] Further, the setscrew 64 provided by an electroconductive
material such as copper and copper alloy allows current
distribution to the electrode pin 58 through the second case 54,
the setscrew 64, the seat 98b, the spring 96 and the seat 98a.
Thus, in addition to the advantages of the above first embodiment,
the first case 92 can be provided by a resin material.
[0064] FIG. 10 is a cross section showing a part of an electrode
unit 100 according to a third embodiment of the present
invention.
[0065] The electrode unit 100 includes a first case 102 and a
second case 104. The first case 102 and the second case 104 are
provided by an electroconductive material such as copper and copper
alloy. The stepped holes 56 of the first case 102 receive the
electrode pins 58 so that the electrode pins 58 are movable back
and forth. A ball plunger 108 serving both as the welding pressure
adjusting mechanism and protrusion adjusting mechanism is screwed
into a threaded hole 106 provided on a second case 104.
[0066] The ball plunger 108 includes a cylindrical thread 110
screwed to the threaded hole 106, a spring 112 disposed inside the
cylindrical thread 110 and a ball 114 disposed at an end of the
cylindrical thread 110. The ball 114 touches the head 58b of the
electrode pin 58.
[0067] According to the above arrangement, the spring 112 is
elastically deformed to adjust the welding pressure of the
electrode pin 58. In addition, the cylindrical thread 110 is
threadably rotated to adjust the stroke of the electrode pin
58.
[0068] Hence, the welding pressure adjusting mechanism and the
protrusion adjusting mechanism in this third embodiment are
provided by a single component (i.e. the ball plunger 108), thus
further simplifying the structure of the electrode unit.
[0069] FIG. 11 is a perspective view showing a relevant part of an
electrode unit 120 according to a fourth embodiment of the present
invention. FIG. 12 is a plan view showing the relevant part of the
electrode unit 120. It should be understood that the fourth
embodiment can be practically applied to the first to third
embodiments.
[0070] The electrode unit 120 includes a first case 122. The first
case 122 is provided with an opening (i.e. a stepped hole 124) in
which the electrode pin 58 is axially slidable. A slitted opening
126 extending in a radial direction of the head 58b of the
electrode pin 58 is provided on an inner wall of the stepped hole
124.
[0071] A slit 128 is provided on the head 58b of the electrode pin
58. A bent or curved metal elastic body (e.g. a plate spring 130)
is disposed in the slit 128 and the slitted opening 126.
[0072] The plate spring 130 is provided by an electroconductive
material such as copper and copper alloy. A central bent portion
130a of the plate spring 130 is in contact with an inner wall of
the head 58b forming the slit 128. Bent portions 130b on both ends
of the plate spring 130 are in contact with a wall forming the
slitted opening 126. Thus, the head 58b of the electrode pin 58 is
continuously pressed toward the inner wall of the stepped hole 124
of the first case 122.
[0073] In this fourth embodiment, the first case 122 and the plate
spring 130 are provided by copper or copper alloy. Thus, electric
current is supplied to the electrode pin 58 via the plate spring
130 that is in contact with the inner wall of the slit 128 of the
electrode pin 58 and the inner wall of the slitted opening 126 of
the first case 122.
[0074] Further, when the electrode pin 58 advances and retracts in
the stepped hole 124, the plate spring 130 is continuously in
electrical connection with the first case 122 and the electrode pin
58. Thus, a contact resistance at the sliding portion can be
maintained at a constant value, so that the electric current can be
securely supplied from the electrode pin 58.
[0075] Incidentally, the metal elastic body may be provided in a
variety of ways. For instance, the metal elastic body may be
provided by bending and curving a rod-shaped spring member instead
of using the plate spring 130.
[0076] Further, though the workpieces are held between the upper
electrode 18 and the lower electrode 20 and are welded at a
plurality of points in the first to fourth embodiments, the present
invention can be also applied in an arrangement in which a pair of
positive and negative electrodes are contacted to the same side of
the workpiece(s) to conduct a multiple-point welding (series
welding).
* * * * *